1. Field of the Invention
This invention relates to a copying lens system suited for copying at a magnification in the vicinity of one-to-one magnification.
2. Description of the Prior Art
Heretofore, a lens system used for copying has usually comprised six to eight lenses disposed symmetrically about a diaphragm with the brightness and aberrations thereof taken into account. In the copying lens system of such construction, if the number of lenses forming the lens system is reduced to reduce the cost thereof and make the system compact, the brightness and aberrations are remarkably deteriorated. For example, if the lens system is formed by four lenses, F-number in such lens system comprising lenses disposed symmetrically about a diaphragm exceeds 9 as known in DAS No. 11 63 045, and the spherical aberration, etc. become greater.
German Patent No. 346029 (published on Dec. 23, 1921) discloses a four-lens lens system having an F-number of 4.5, but the present invention provides a copying lens system in which aberrations are further improved.